// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_BREAK_LIST_H_
#define UI_GFX_BREAK_LIST_H_

#include <stddef.h>

#include <utility>
#include <vector>

#include "base/logging.h"
#include "ui/gfx/range/range.h"

namespace gfx {

// BreakLists manage ordered, non-overlapping, and non-repeating ranged values.
// These may be used to apply ranged colors and styles to text, for an example.
//
// Each break stores the start position and value of its associated range.
// A solitary break at position 0 applies to the entire space [0, max_).
// |max_| is initially 0 and should be set to match the available ranged space.
// The first break always has position 0, to ensure all positions have a value.
// The value of the terminal break applies to the range [break.first, max_).
// The value of other breaks apply to the range [break.first, (break+1).first).
template <typename T>
class BreakList {
public:
    // The break type and const iterator, typedef'ed for convenience.
    typedef std::pair<size_t, T> Break;
    typedef typename std::vector<Break>::const_iterator const_iterator;

    // Initialize a break at position 0 with the default or supplied |value|.
    BreakList();
    explicit BreakList(T value);

    const std::vector<Break>& breaks() const { return breaks_; }

    // Clear the breaks and set a break at position 0 with the supplied |value|.
    void SetValue(T value);

    // Adjust the breaks to apply |value| over the supplied |range|.
    void ApplyValue(T value, const Range& range);

    // Set the max position and trim any breaks at or beyond that position.
    void SetMax(size_t max);
    size_t max() const { return max_; }

    // Get the break applicable to |position| (at or preceeding |position|).
    typename std::vector<Break>::iterator GetBreak(size_t position);
    typename std::vector<Break>::const_iterator GetBreak(size_t position) const;

    // Get the range of the supplied break; returns the break's start position and
    // the next break's start position (or |max_| for the terminal break).
    Range GetRange(const typename BreakList<T>::const_iterator& i) const;

    // Comparison functions for testing purposes.
    bool EqualsValueForTesting(T value) const;
    bool EqualsForTesting(const std::vector<Break>& breaks) const;

private:
#ifndef NDEBUG
    // Check for ordered breaks [0, |max_|) with no adjacent equivalent values.
    void CheckBreaks();
#endif

    std::vector<Break> breaks_;
    size_t max_;
};

template <class T>
BreakList<T>::BreakList()
    : breaks_(1, Break(0, T()))
    , max_(0)
{
}

template <class T>
BreakList<T>::BreakList(T value)
    : breaks_(1, Break(0, value))
    , max_(0)
{
}

template <class T>
void BreakList<T>::SetValue(T value)
{
    breaks_.clear();
    breaks_.push_back(Break(0, value));
}

template <class T>
void BreakList<T>::ApplyValue(T value, const Range& range)
{
    if (!range.IsValid() || range.is_empty())
        return;
    DCHECK(!breaks_.empty());
    DCHECK(!range.is_reversed());
    DCHECK(Range(0, max_).Contains(range));

    // Erase any breaks in |range|, then add start and end breaks as needed.
    typename std::vector<Break>::iterator start = GetBreak(range.start());
    start += start->first < range.start() ? 1 : 0;
    typename std::vector<Break>::iterator end = GetBreak(range.end());
    T trailing_value = end->second;
    typename std::vector<Break>::iterator i = start == breaks_.end() ? start : breaks_.erase(start, end + 1);
    if (range.start() == 0 || (i - 1)->second != value)
        i = breaks_.insert(i, Break(range.start(), value)) + 1;
    if (trailing_value != value && range.end() != max_)
        breaks_.insert(i, Break(range.end(), trailing_value));

#ifndef NDEBUG
    CheckBreaks();
#endif
}

template <class T>
void BreakList<T>::SetMax(size_t max)
{
    typename std::vector<Break>::iterator i = GetBreak(max);
    i += (i == breaks_.begin() || i->first < max) ? 1 : 0;
    breaks_.erase(i, breaks_.end());
    max_ = max;

#ifndef NDEBUG
    CheckBreaks();
#endif
}

template <class T>
typename std::vector<std::pair<size_t, T>>::iterator BreakList<T>::GetBreak(
    size_t position)
{
    typename std::vector<Break>::iterator i = breaks_.end() - 1;
    for (; i != breaks_.begin() && i->first > position; --i)
        ;
    return i;
}

template <class T>
typename std::vector<std::pair<size_t, T>>::const_iterator
BreakList<T>::GetBreak(size_t position) const
{
    typename std::vector<Break>::const_iterator i = breaks_.end() - 1;
    for (; i != breaks_.begin() && i->first > position; --i)
        ;
    return i;
}

template <class T>
Range BreakList<T>::GetRange(
    const typename BreakList<T>::const_iterator& i) const
{
    const typename BreakList<T>::const_iterator next = i + 1;
    return Range(i->first, next == breaks_.end() ? max_ : next->first);
}

template <class T>
bool BreakList<T>::EqualsValueForTesting(T value) const
{
    return breaks_.size() == 1 && breaks_[0] == Break(0, value);
}

template <class T>
bool BreakList<T>::EqualsForTesting(const std::vector<Break>& breaks) const
{
    if (breaks_.size() != breaks.size())
        return false;
    for (size_t i = 0; i < breaks.size(); ++i)
        if (breaks_[i] != breaks[i])
            return false;
    return true;
}

#ifndef NDEBUG
template <class T>
void BreakList<T>::CheckBreaks()
{
    DCHECK_EQ(breaks_[0].first, 0U) << "The first break must be at position 0.";
    for (size_t i = 0; i < breaks_.size() - 1; ++i) {
        DCHECK_LT(breaks_[i].first, breaks_[i + 1].first) << "Break out of order.";
        DCHECK_NE(breaks_[i].second, breaks_[i + 1].second) << "Redundant break.";
    }
    if (max_ > 0)
        DCHECK_LT(breaks_.back().first, max_) << "Break beyond max position.";
}
#endif

} // namespace gfx

#endif // UI_GFX_BREAK_LIST_H_
